Yes. Now make that thumb a little larger by extending the length from the large joint to about matching the ring finger length. Next thicken it from the thumb finger print area pad on up to the palm. The thumb is largest digit in the human hand. It is not currently represented that way. And, foreshortening is an entirely different topic.

Pretty good start .. Proportion tip that I use,, Wrist is roughly the same width of all four fingers put together. Thumb length reaches the top of first Phalange (knuckle) of your index finger. Agree with Carl... Foreshortening is totally different. This aspect (view) of the hand is direct... you don't have to worry about Foreshortening here. Keep going.